There has been a demand for higher speed communication and larger communication data capacity in recent wireless communication technology. A MIMO-OFDM technique combining multi input multi output (MIMO) and orthogonal frequency division multiplexing (OFDM) has attracted attention in response to such a demand. MIMO is a technique using a plurality of antennas by both a transmitter and a receiver, and OFDM is a modulation technique that is used in next-generation mobile communication such as long term evolution (LTE) due to its excellent bandwidth efficiency and high tolerance to the multipath fading environment.
An example of a receiver of the MIMO technique is disclosed in Japanese Unexamined Patent Application Publication No. 2004-179822 (paragraphs [0003] to [0008]).
According to Japanese Unexamined Patent Application Publication No. 2004-179822, in the MIMO technique, signals transmitted from transmitting antennas are received by receiving antennas, and a propagation path between the transmitting and receiving antennas is estimated based on known signals for estimating the propagation path, which are inserted in the signals received by the receiving antennas. The estimated propagation path is represented by a matrix based on the number of antennas of both the transmitter and the receiver. An inverse matrix of the propagation path is multiplied by the signals received by the receiving antennas, whereby the signals transmitted from the transmitting antennas are obtained.